OneSteel is an Australian-base mining, ore processing and steel manufacturing company specialising in long-steel products for the construction, housing and agricultural industries. The company is a former subsidiary of BHP and was separated from the parent company as part of its corporate restructure in October 2000; the parent went on to merge with Billiton to form the company BHP Billiton, the world's largest mining company. Onesteel comprises 0.23% of the S&P/ASX 200 index.